Variable pressure insulation piercing crimp



J. B.' soLA ETAL 3,077,027

Feb. 12, 1963 VARIABLE PRESSURE INSULATION PIERCING CRIMP Filed Feb. 5, 1958 vINVENTORS Jo/m B. .9o/a H/'c/mrd [Krause 49W mmgn Mm United States Patent Otice .'.iiii Patented Feb. l2, i953 3,977,627 VARABLE PESl-URE NSULATEUN NERGENS CREME n Soia and Richard '7. Krause, Chicago, Ill., as-

rors to Maico Manufacturing Company, Chicago, `il., a partnership consisting ot Ai .lust and Margaret R.

ust

Filed Feb. 5, i953, Ser. No. 713,413 3 Claims. (Si. TIL-155.55)

The present invention relates to terminal connectors for electrical wires. More particularly, the invention relates to improved wire crimps for securing pierce-type terminals to insulated wires and to the method for torming the wire crimps.

In the pierce-type of terminal connector according to the present invention, one or more prongs or barbs are provided in the wire Grip portion which pierce the insulation of the wire and make electrical contact with the conducting core when the terminal connector is crimped on the wire. Piercer/pe connectors of the prior art provide crimping arms directly over the insulation piercing prongs in order to malte certain that the prongs pierce the insulation and make proper electrical contact with the wire. Such connectors are subject to a number of limitations, particularly in that different terminal connector sizes are required for each different size of wire. This is because prongs must be long enough to make the proper electrical contact with the wire, but at the same time they should not be long enough to pierce the other side of the insulation, since this would reduce the tensile strength of the wire and would provide undesirable, additional insulation breaks. rFlins, heretofore it has been necessary for terminal users and dealers to carry large stocks of terminals ot various sizes to accommodate a wide variety of wire sizes.

Accordingly, it is an object of the invention to provide an improved pierce-type terminal wire crimp.

Another object of the invention is to provide a piercetype terminal in which the force required to pull thev wire from the terminal is substantially equal to the ultimate strength of the wire.

A further object of the invention is to provide a piercetype terminal in which the insulation piercing barbs are disposed between the crimping arms rather than under the crimping arms.

A still further object of the invention is to provide an improved pierce-type terminal in which the insulation piercing prongs are substantially longer than was possible in earlier pierce-type terminals.

Still another object of the invention is to provide a pierce-type terminal in which the insulation piercing barbs are disposed below a variable pressure clamping arm, the position of which is varied in accordance with the size of the wire beinr7 crimped to insure electrical Contact between the barbs and the wire while preventing piercing ofthe opposite side ofthe insulation.

An important object of the invention is to provide an improved piercetype terminal in which one size of the terminal can be utilized for crimping to a variety of sizes of wires to drastically reduce stocks of terminals which must be maintained.

Another object of the invention is to provide a method for forming a variable pressure pierce-type terminal connector for crimping a single size of terminal on a variety of sizes of wires.

A further object of the invention is to provide a method for forming an improved pierce-type crimp in which a pair of crimping arms of a terminal are iirmly crimped about an insulated wire with at least one insulation pierc ing barb axially spaced between the crimping arms, to

permit the insulation between the arms to bulge to prevent the barb from piercing both sides of the insulation.

A still further object ot the invention is to provide a method according to the previous object in which the amount `of bulge between the crimping arms is controlled during crimping by applying a pressure determined by the size relationship between the wire and the terminal.

Other objects, features and advantages will be apparent from the foregoing detailed description, tak-en in conjunction with the accompanying drawings, in which:

FIGURE 1 is a perspective View of a pierce-type terminal connector in accordance with the present invention, shown crimped to a section of insulated Wire;

FIGURE 2 is a perspective view of a terminal connector according to FlGURE 1 before the connector has been crimped to a wire;

FGURE 3 is a top view of the terminal of FIGURE 2;

FiGURE 4 is a sectional View taken substantially along line 4i or" FiGURE l;

FiGURE 5 is a sectional View similar to FIGURE 4 but showing the same terminal crimped to a substantially larger wire;

FIGURE 6 is a sectional view of a pierce-type terminal of the prior art shown crimped to a section of proper size wire;

FEGURE 7 is a sectional View similar to FIGURE 6 but showing the same prior art terminal inadequately crimped to a Wire the size of that shown in FIGURE 5;

FIGURE 8 is a perspective view similar to FIGURE l but illustrating a moditied form of terminal connector with the center clamping arm eliminated;

FIGURE 9 is a sectional view taken substantially along line 9-9 of FlGURE 8.

The pierce-type terminal connector illustrated in FlG- URES 1-5 is generally designated by the reference numeral iii. The terminal is formed orr sheet metal of good electrical conductivity and includes a contact portion l2 and an integral Wire grip portion 11i. While the contact portion shown is of the forked type for connecting to a terminal post or the like (not shown), it should be understood that any desired type of contact portion may be employed.

The Wire grip portion lli has a errule-lihe conf guration which is tightly formed about a section of an insulated electrical wire 16. The wire may be of any standard construction having electrical insulation 18 formed about a central, electrical conductin'J core 26, which is preterably stranded as shown.

The wire grip portion is provided with a pair of integral crimping arms 2.2, 22 which are axially spaced and which extend from one edge portion of a body or bight 2d ot generally U-shaped cross-section. A central integral clamping arm Z6 extends from the other edge portion of the bight Z4 and is axially spaced between the crimping arms 22.

A pair of upstanding, integral insulation piercing prongs .or barbs 23, 28 are formed from the metal of the bight 24, and it Will be noted that the barbs are axially spaced between the crimping arms 22,. Thus, the prongs are axially located in the area of the clamping arm 26, in the bottom of the bight. The barbs may be conventionally formed by punching them from the metal of the bight and bending them so that they extend upwardly with respect to the bottom of the bight, in a generally radial direction. The barbs are preferably pointed at their upper ends, as shown, leaving triangular cut-outs 3i? in the adi-scent portions of the bight.

The terminal connector l@ is crimped to a section of the insulated Wire i6 by bending the crimping arms 2?. and the clamping arm 26 about a portion of the wire, usually the end portion, which is disposed in the bight 2d.

In FIGURE 4 a terminal connector of a given size is shown crimped to the insulated Wire i6, of relatively small size, while in the illustration of FIGURE 5 the same size terminal is shown crimped to a wire 16a of considerably larger size with thicker insulation. In both 4cases the crimping arms 22 are crimped tightly about the wire to rmly secure the terminal to the wire. The pressure-which is brought to bear is sufficient that the strength of the connection, or its maximum pull test strength, is substantially equal to the tensile strength of the wire. This impels a portion 32 of the insulation between the crimping arms 22 not confined by the bight 24 to bulge substantially. When the terminal is crimped to a small size wire as shown in FIGURE 4, this bulge provides clearance for the upper ends of the prongs 28, which can thus be `made substantially longer than would otherwise be possible. At substantially the same time that the crimping arms 22 are crimped about the wire, the clamping arm 26 is crimped about the insulation portion 32, but with controlled, predetermined pressure to insure that the barbs pierce only the lower portion of the insulation and make proper electrical contact with the core of the wire. In other words, the clamping arm is crimped with sufficient pressure to force the barbs through the lower portion ofthe insulation and through the core of thewire, but this pressure is not sucient to cause the barbs to pierce the upper portion 32 of the insulation. The barbs should penetrate more than half wayrthrough the core for proper electrical contact, and it is preferable that they extend through the full diameter of the core as shown.

lf the pressure brought to bear on the clamping arm 26 of FIGURE 4 were to be increased so that the clamping arm would be brought down to the level of the crimping arms 22, it is readily apparent that the oversize barbs 28 would pierce the portion 32 of the insulation of the small diameter wire 16, thus reducing the strength of the wire and causing unnecessary breaks in the insulation. However, where the terminal is crimped to the relatively large size wire 16a as shown in FIGURE 5, the clamping arm 26 is crimped with greater pressure to reduce or eliminate the bulge in the insulation, to insure that the core of the wire is pierced sufficiently by the barbs to provide good electrical contact.

In order to more graphically illustrate the effectiveness of the present invention, a typical pierce-type terminal 4t) of the prior art is illustrated in FiGURES 6 and 7. rl`his terminal may include a bight 42 having integral crimping -arms 46 overlying a pair of insulation piercing barbs or prongs 44. The barbs of the prior art terminal are placed directly belowthe crimping arms, so that when the arms' are crimped about the wire to hold the terminal thereon, the wire is forced onto the barbs at the same time, insuring that they pierce the insulation and make sutiicient electrical contact with the core. ln other words, then, the prior art crimping arms 46 pei'- form a two-fold function in holding the terminal on the wire and incausing the barbs to piercethe insulation and make electrical contact. Because of this two-fold function performed by the crimping arms 46, the barbs rnust be directly below the crimping arms as shown. l

inasmuch as the prior art clamping arms mustbe crimped about the wire sufficiently tight to hold the ter# minal on the wire, it is not possible to reduce the pressure applied by these arms in order to accommodate longer insulation piercing prongs. Consequently, the conventional prongs must be quite short, as shown, and it follows that each terminal must be 4designed for clamping to a given size of wire, such as the small Wire 16. It the lterminal isV crimped to -a substantially larger size wire, such as the wire 16a, the barbs'are much too short to pierce the thicker insulationuand make proper electrical contact with the largercore, as clearly shown in FIGURE 7-.` Furthermore, it isV not possible to apply a* substantially larger pressure through the prior art crimping arms. 46 when crimping a terminal on a large size.

wire, because this would crush the wire and cut the insulation.

According to the method of the present invention, a terminal blank is formed similar to that shown in FIG- URE 2, having outer crimping arms 22 and a central clamping arm 26 which is adapted to overlay centrally located insulation piercing prongs. The next step is to' insert a section of insulated wire in the bightof the terminal and to crimp the crimping arms tightly about the Wire with sucient pressure to insure that the pull-out strength of the wire is substantially equal to its tensile strength. The next step, which is performed at substantially the same time as the previous step, is to crimp the vari-able pressure clamping arm 26 about the exposed portion of the insulation between the crimping arms with a predetermined pressure suited to the wire size and the terminal size, sucient to cause the prongs to pierce the lower side of the insulation and to make proper electrical contact with the core, but insufficient to cause the prongs to pierce the upper side of the insulation. be performed by hand, using hand tools, but it is preferable to utilize a suitable crimping machine with diens (not shown) properly set to perform the particular crimping operation swiftly and uniformly.

It is possible to eliminate the central clamping arm 26 and instead to press directly against the exposed surface 32 of the insulation. In other words, the tool (not shown) which would ordinarily crimp the clamping arm 26 can` instead be brought down sufficiently to press against the exposed surface of the insulation with predetermined pressure suiicient to cause the prongs to penetrate the wire to the proper depth. Such a modified embodiment ofterminal is shown in FIGURES 8 and 9, and is generally designated by the reference numeral 10a. In this embodiment the bulged insulation 32 is exposed, but the height of the bulge was determined by the forming tool- (not shown) when the terminal Was crimped on the wire. Thus, in this embodiment, a controlled size' of bulge is provided by applyingpredetermined pressure directly against the exposed insulation, thus obtaining the same benets explained in connection with the rst ernbodiment.

The application of controlled presure, through the clamping arm 26 or directly against the exposed insulation, prevents tearing or cutting of the insulation adjacent the' crimping arms, thus permitting application of a somewhat greater crimping pressure through the crimping arms 22.

From the foregoing description it will be readily ap parent that the present invention provides an improved pierce-type terminal and an improved method for forming the same in which a terminal of one size can be crimped to a variety of sizes of wires, having a variety of thier.I nesses of insulation, by controlling the pressure applied to the wire to cause the prongs to pierce the insulation and to make electrical contact. This is made possible by placing the insulation piercing prongsbetween the crimp-I ing arms to take advantage of the tendency of the in-' sulation to bulge, thus permitting the use of insulation piercing prongs which are considerably longer than would otherwise be possible. The provision of oversize prongs together with application of controlled pressure on the insulation over the ends of the prongs allows drastic reduction in the number of sizes of terminals which must be produced and stocked, and, consequently, provides a great saving in time, material and manpower.

Variations and modilications may be effected without departing from the scope of the'novel concepts of the present invention.

We claim:

minimum diameter to a predetermined maximum diam* It will be readily apparent that the method couldy eter through controlling bulging of the crimped Wire, comprising the steps of forming a terminal having at least one insulation piercing prong and crimping means axially spaced on each side of said prong, said prong having a length which is greater than one-half the diameter of the bare wire plus the thickness of the insulation on one side of the maximum diameter wire but is no greater than the diameter of the bare wire plus the thickness of the insulation plus the increase in thickness due to bulging of the minimum diameter Wire, crimping said terminal to the wire with a relatively high presure to secure the terminal thereon and to induce the insulation to bulge in an area opposite to said prong, and pressing said insulation in said area with a controlled pressure dierent from and unrelated to said high pressure to cause the prong to pierce the insulation only on the side opposite to said area and to penetrate more than half way through the core of the wire to make good electrical contact with the core.

2. A method of crimping a metallic terminal to an insulated wire in a range of sizes from a predetermined minimum diameter to a predetermined maximum diameter through controlling bulging of the crimped Wire, comprising the steps of forming a terminal having at least one insulation piercing prong and a pair of crimping arms axially spaced on each side of said prong, said prong having a length which is greater than one-half the diameter of the bare wire plus the thickness of the insulation on one side of the maximum diameter wire but is no greater than the diameter of the bare wire plus the thickness of the insulation plus the increase in thickness due to bulging of the minimum diameter wire, crimping said arms about said wire to clamp the terminal to the -wire with a relatively high pressure while permitting the insulation of the Wire between the arms to bulge, and pressing the bulged insulation with a controlled pressure different from and unrelated to said high pressure to cause the prong to pierce the insulation only on the side opposite and to penetrate more than half way through the core of the wire to make good electrical contact with the core.

3. A method of crimping -a metallic terminal to an insulated wire in a range of sizes from a predetermined minimum diameter to a predetermined maximum diameter through controlling bulging of the crimped Wire, comprising the steps of forming a terminal having at least one insulation piercing prong With a pair of crimping arms `axially spaced on each side of said prong and a central clamping arm between said crimping arms, said prong having a length which is greater than one-half the diameter of the bare wire plus the thickness of the insulation on one side of the maximum diameter vvire but is no greater than the diameter of the bare wire plus the thickness of the insulation plus the increase in thickness due to bulging of the minimum diameter wire, crimping said crimping arms about said wire to clamp the terminal to the wire with a relatively high pressure While per mitting the insulation of the wire between the crimping arms to bulge, and forming said clamping arm about the bulged insulation with a controlled pressure different from and unrelated to said high pressure to cause the prong to pierce the insulation on the side of the wire opposite to the bulged insulation only and to penetrate more than half way through the core of the wire to make good electrical contact with the core.

References Cited in the le of this patent UNITED STATES PATENTS 1,070,948 Dodd Aug. 19, 1913 1,160,534 Schmidt Nov. 16, 1915 2,309,311 Grohsgal Jan. 26, 1943 2,501,870 Malhiot Mar. 28, 1950 2,680,235 Pierce .lune 1, 1954 2,727,299 Klumpp Dec. 20, 1955 2,802,257 Holtzapple Aug. 13, 1957 2,814,026 Broske Nov. 19, 1957 2,982,938 Klumpp May 2, 1961 FOREIGN PATENTS 617,955 France Nov. 3, 1926 

1. A METHOD OF CRIMPING A METALLIC TERMINAL TO AN INSULATED WIRE IN A RANGE OF SIZES FROM A PREDETERMINED MINIMUM DIAMETER TO A PREDETERMINED MAXIMUM DIAMETER THROUGH CONTROLLING BULGING OF THE CRIMPED WIRE, COMPRISING THE STEPS OF FORMING A TERMINAL HAVING AT LEAST ONE INSULATION PIERCING PRONG AND CRIMPING MEANS AXIALLY SPACED ON EACH SIDE OF SAID PRONG, SAID PRONG HAVING A LENGTH WHICH IS GREATER THAN ONE-HALF THE DIAMETER OF THE BARE WIRE PLUS THE THICKNESS OF THE INSULATION ON ONE SIDE OF THE MAXIMUM DIAMETER WIRE BUT IS NO GREATER THAN THE DIAMETER OF THE BARE WIRE PLUS THE THICKNESS OF THE INSULATION PLUS THE INCREASE IN THICKNESS DUE TO BULGING OF THE MINIMUM DIAMETER WIRE, CRIMPING SAID TERMINAL TO THE WIRE WITH A RELATIVELY HIGH PRESSURE TO SECURE THE TERMINAL THEREON AND TO INDUCE THE INSULATION TO BULGE IN AN AREA OPPOSITE TO SAID PRONG, AND PRESSING SAID INSULATION IN SAID AREA WITH A CONTROLLED PRESSURE DIFFERENT FROM AND UNRELATED TO SAID HIGH PRESSURE TO CAUSE THE PRONG TO PIERCE THE INSULATION ONLY ON THE SIDE OPPOSITE TO SAID AREA AND TO PENETRATE MORE THAN HALF WAY THROUGH THE CORE OF THE WIRE TO MAKE GOOD ELECTRICAL CONTACT WITH THE CORE. 